Did you know? #clojure

binding-conveying.clj

;; did you know that binding conveying is not immutable but read-only? (the future sees updates performed by the original thread)
=> (with-local-vars [a 1]
     (future (Thread/sleep 1000) (prn 'future @a))
     (var-set a 2))
2
future 2

;; you have to push new bindings to isolate:
=> (with-local-vars [a 1]
     (with-bindings {a @a}
       (future (Thread/sleep 1000) (prn 'future @a)))
     (var-set a 2))
2
future 1

;; but it's a var-by-var isolation:
=> (with-local-vars [a 1
                     b 'one]
     (with-bindings {a @a}
       (future (Thread/sleep 1000) (prn 'future @b)))
     (var-set b 'two))
two
future two

;; to completely isolate from upstream changes, one has to do:
=> (with-local-vars [a 1
                     b 'one]
     (with-bindings (get-thread-bindings)
       (future (Thread/sleep 1000) (prn 'future @b)))
     (var-set b 'two))
two
future one